Structural determination of the acidic exopolysaccharide produced by a Pseudomonas sp strain 1.15

Pseudomonas strain 1.15 was isolated from a freshwater biofilm and shown to produce considerable amounts of an acidic polysaccharide which was investi gated by methylation analysis, NMR spectroscopy and ionspray mass spectrome try (ISMS). The polysaccharide was depolymerised by a bacteriophage-associa ted endoglucosidase and by autohydrolysis, and the resulting oligosaccharid es were investigated by NMR spectroscopy and mass spectrometry. The resulti ng data showed that the parent repeating unit of the 1.15 exopolysaccharide (EPS) is a branched hexasaccharide. The main chain is constituted of the t risaccharide --> 4)-alpha-L-Fucp-(1 --> 4)-alpha-L-Fucp-(1 --> 3)-beta-D-Gl cp(1 --> and the side chain alpha-D-Galp-(1 --> 4)-beta-D-GlcAp-(1 --> 3)-a lpha-D-Galp-(1 --> is linked to O-3 of the first Fuc residue. The terminal non-reducing Gal carries a 1-carboxyethylidene acetal in the R configuratio n at the positions 4 and 6. Of the four different O-acetyl groups present i n non-stoichiometric amounts, two were established to be on O-2 of the 3-li nked Gal and on O-2 of the 4-linked Fuc. (C) 1999 Elsevier Science Ltd. All rights reserved.